1. Field of the Invention
The present invention relates to an Ad-hoc network, and more particularly relates to an area limited Ad-hoc network and data transfer in the area limited Ad-hoc network.
2. Description of the Related Art
An Ad-hoc network is a kind of wireless multi-hop network. Compared to a conventional wireless network, the Ad-hoc network is not dependent on any fixed infrastructure and administration center. That is to say, the Ad-hoc network is temporarily formed by a group of independent mobile nodes (for example, notebook computers or personal digital assistants), and according to cooperation between the mobile nodes and self-organization of themselves, network connection is kept and data transfer is achieved. A conventional Ad-hoc network does not have a predetermined (for example, artificially defined) boundary to limit (define) an area; in general, the area is limited by a maximum transfer distance (length) of the Ad-hoc network.
From a viewpoint of considering communications security and the like, Ricoh Co., Ltd. has made some studies on an area limited Ad-hoc network, and has proposed achieving area limitation by using, for example, infrared rays (IR), Near Field Communications (NFC), ultrasonic waves, microwaves, or the like. Since an area limited Ad-hoc network has a predetermined boundary, compared to the conventional Ad-hoc network, a mobile node may enter or exit from the area, and communications may be carried out between mobile nodes only located in the same area. As a result, how to determine whether a mobile node is located in an area limited Ad-hoc network as well as how to achieve energy (electric power) consumption optimized data transfer between mobile nodes located in the same area limited Ad-hoc network becomes a problem that needs to be solved at present.